Containment systems, including inner and outer packaging, have significantly improved during the twenty-five (25) years since the inception of regulations governing the treatment, packaging, and transportation of Regulated Medical Waste. Containment systems for preventing liquid (e.g., blood and bodily fluids) spillage and sharps (e.g., needles, glass, scalpels, etc.) exposure for avoidance of puncture wounds have made great strides in efficacy. These systems have triggered a re-evaluation of the treatment model for autoclaves. The “desk top” laboratory autoclaves have been replaced with pressure vessels that can process more than 2,000 pounds a cycle. Where “direct impingement” of steam on the waste to obtain biological kill temperatures and a “surface contact” model were appropriate, container evolution and waste mass now dictate the concept of a “Thermal Transfer” model. Autoclaves are classified as thermal deactivation devices in relation to biological kill measurements. Accordingly, maximizing steam penetration to cause rapid rise to the needed kill temperatures is essential to optimum process success.
Air contained within the containment systems used to hold Regulated Medical Waste and within the autoclave (pressure vessel) used for treating Regulated Medical Waste acts as an insulator. Historically, after placing the Regulated Medical Waste in the autoclave (pressure vessel), a vacuum was drawn in the autoclave to remove air from the autoclave prior to treating the Regulated Medical Waste with steam in the autoclave. Following the drawing of a vacuum in the autoclave, steam injection into the autoclave was initiated to treat the Regulated Medical Waste placed in the autoclave with steam. Steam injection piping systems for injecting steam into the autoclave generally included in series along the piping from the main steam line to the autoclave a manual isolation valve, followed by an automated control valve, followed by a steam pressure reducer for lowering the facility's main steam pressure to the lower autoclave operating pressure. Following the pre-treatment vacuum and the initial injection of steam into the autoclave through the steam injection piping system, a static head (constant pressure) was maintained in the autoclave until the completion of the steam treatment cycle. The static head (constant pressure) was maintained in the autoclave by having the steam pressure reducer in line with the manual isolation valve and the automatic control valve, and having the manual isolation valve and the automated control valve open throughout the steam treatment cycle, the injection of new steam, and the thermal energy contained therein, into the autoclave via the steam injection piping system being dependent on the condensation rate in the autoclave during the steam treatment cycle. After the steam treatment cycle and cessation of steam injection, a post treatment cycle vacuum was drawn to flash off condensation.
Our research has determined that autoclaves (pressure vessels) operating as described in the previous paragraph do not provide consistent biological kill. The variations in mass, liquid quantities, porosity, and containment systems are not answered by a one single, set treatment cycle unless that cycle assumes the combined maximums in weight, liquid content, porosity, and containment system strength associated with the waste stream typical of that specific facility. Multiple data inputs are required to vary an autoclave's “residence time” (the time duration at or above the minimum biological kill temperature stipulated by regulations) to respond to these parametric variations. Robert W. Lewis' U.S. Pat. Nos. 6,867,393 and 7,815,851, which are incorporated herein by reference, and Robert W. Lewis' U.S. patent application Ser. No. 12/924,438, which also is incorporated herein by reference, disclose improvements relating to the treatment of Regulated Medical Waste to enhance the efficacy of such treatment, such as:
(a) varying process times, including residence time that the waste to be sterilized is exposed to steam in the autoclave, process temperatures, and process pressures, including vacuum for negative pressure and steam injection for positive pressure, to predetermined settings (determined empirically by testing the facility's waste stream) that correlate to the waste character profile (e.g., “bagged waste”, “laboratory waste”, or “suction canister waste”) of the waste to be treated and to the weight (mass) of the waste to be treated, and
(b) enhancing steam penetration and containment system disruption by using multiple vacuum/steam injection pulses.
Continuous condensation removal, as detailed in our U.S. patent application Ser. No. 11/904,417, which is incorporated herein by reference, increases autoclave efficacy by enhancing uniform biological kill throughout an autoclave.